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| United States Patent |
6,132,048
|
|
Gao
, et al.
|
October 17, 2000
|
Single display assembly having selective reflectors to view indicia
Abstract
A single display assembly (10) has an electronically controllable display
(11) with a plurality of display elements (12) and sandwiched by two
support plates (13,14), two polarizers (15,16) and two selective
reflectors, namely a first selective reflector (17) and a second selective
reflector (18). Support plates (13,14) and polarizers (15,16) are
transparent media to permit passage of light. Selective reflectors (17,18)
are holographic reflectors that are each pre-recorded with characteristics
that includes a range (19 or 20) of predetermined incident angles relative
to inward facing horizontal surfaces (24,25) and an angular transparency
range (not shown) for passage of light. Assembly (10) has two opposite
sides (21,22) to view indicia provided by display elements (12). Indicia
can be selectively viewed from either of sides (21 or 22) without
interference from external background of a remaining one of sides (21 or
22).
| Inventors:
|
Gao; Qi (Singapore, SG);
Peana; Stefan (Singapore, SG)
|
| Assignee:
|
Motorola (Schaumburg, IL)
|
| Appl. No.:
|
393282 |
| Filed:
|
September 10, 1999 |
| Current U.S. Class: |
353/20; 349/61; 349/62; 353/122; 359/15 |
| Intern'l Class: |
G03B 021/28; G02F 001/133.5 |
| Field of Search: |
353/20,120,122,DIG. 3
349/61,16,62,162,113
359/15
|
References Cited
U.S. Patent Documents
| 5115228 | May., 1992 | Harris et al.
| |
| 5353075 | Oct., 1994 | Conner et al. | 353/122.
|
| 5712694 | Jan., 1998 | Taira et al. | 349/62.
|
| 5812229 | Sep., 1998 | Chen et al. | 349/117.
|
| 5828488 | Oct., 1998 | Ouderkirk et al. | 349/62.
|
| 5853240 | Dec., 1998 | Tanaka et al. | 353/20.
|
| 6044196 | Mar., 2000 | Winston et al. | 349/61.
|
Primary Examiner: Dowling; William
Attorney, Agent or Firm: Macnak; Philip P.
Claims
What is claimed is:
1. A single display assembly having selective reflectors, said assembly
comprising:
an electronically controllable display; and
at least two selective reflectors including a first selective reflector and
a second selective reflector, said display being sandwiched by said
selective reflectors,
wherein incident light passing through said first selective reflector and
said display is reflected back by said second selective reflector through
said display and said first selective reflector, said incident light being
received within a range of predetermined incident angles relative to an
inward facing horizontal surface of said first selective reflector.
2. The assembly as claimed in claim 1 wherein incident light passing
through said second selective reflector and said display is reflected back
by said first selective reflector through said display and said second
selective reflector, said incident light being received within a range of
predetermined incident angles relative to an inward facing horizontal
surface of said second selective reflector.
3. The assembly as claimed in claim 1 wherein one of said selective
reflectors has an angular transparency range associated with said range of
predetermined incident angles of the other of said reflectors.
4. The assembly as claimed in claim 1 wherein said selective reflectors are
holographic reflectors.
5. The assembly as claimed in claim 1 wherein each of said holographic
reflectors comprises one or more layers of holographic elements.
6. The assembly as claimed in claim 1 and further comprising at least two
transparent media.
7. The assembly as claimed in claim 6 wherein said transparent media
includes polarizers.
8. The assembly as claimed in claim 6 wherein said transparent media
includes support plates.
9. The assembly as claimed in claim 1 and further comprising at least one
light guide having at least one light source respectively coupled thereto,
said selective reflectors being sandwiched by said at least one light
guide.
Description
FIELD OF THE INVENTION
This invention relates to display assemblies for electronic display
devices. In particular, this invention relates to, but is not necessarily
limited to, a single display assembly having selective reflectors to view
indicia.
BACKGROUND OF THE INVENTION
Display assemblies of electronic display devices that provide indicia using
display elements such as liquid crystals are known. For example, indicia
are provided in a conventional liquid crystal display (LCD) assembly by
selectively actuating liquid crystals to control passage of light. Such a
conventional LCD assembly includes transparent media, such as glass or
plastics, to sandwich one or more layers of such liquid crystals.
Light required to form the indicia with liquid crystals has to pass through
the liquid crystals to a viewer. Such light is typically provided with
either a light source or ambient light. The light source can placed to the
rear of an LCD assembly so that the light generated can pass through the
liquid crystals of the LCD assembly to the viewer. Such a light source
provides what is commonly referred to as backlighting. Alternatively, the
light source can be placed in front of the liquid crystals. Placed as such
to provide frontlighting, which is similar to how ambient light is
provided, the light that is generated has to pass through the liquid
crystals to be reflected back to the viewer. With frontlighting or ambient
light, the LCD assembly requires a reflector, placed on the other side of
the liquid crystals relative to the light source, to reflect the light
back to the viewer.
Viewing from both sides of an LCD assembly is desirable in applications
such as, for example, a portable electronic device that is folded to
reduce its size when not in use. For such applications, being viewable
from an opposite side enables a user to preview indicia without having to
unfold the portable electronic device. However, a problem with viewing a
conventional LCD assembly from opposite sides is that the LCD assembly
must then permit passage of light through both opposite sides and, as
such, external background not related to the indicia on one side can then
be seen from an opposite side. Such background is undesirable because it
tends to interfere with viewing from the opposite side. Conventional
reflectors to block the external background on one side does not overcome
this problem as these will also block incident light required to view
indicia from that one side.
To overcome the above problem, U.S. Pat. No. 5,115,228 describes electronic
shutters of liquid crystal emulsion flashing rapidly to enable viewing of
information from opposite surfaces of a display. However, such electronic
shutters require complex driving circuitry to control timing of the
flashing and to process the information. Providing two separate LCD
assemblies may solve the problem but substantially increases the cost of
the assembly and, furthermore, additional space is required which is
undesirable for use in, for example, portable electronic devices. Hence, a
need exists for a single display assembly to provide indicia that are
viewable from opposite sides without requiring relatively complex driving
circuitry or additional costs.
SUMMARY OF THE INVENTION
According to one aspect of the invention, there is provided a single
display assembly having selective reflectors, said assembly comprising:
an electronically controllable display; and
at least two selective reflectors including a first selective reflector and
a second selective reflector, said display being sandwiched by said
selective reflectors,
wherein incident light passing through said first selective reflector and
said display is reflected back by said second selective reflector through
said display and said first selective reflector, said incident light being
received within a range of predetermined incident angles relative to an
inward facing horizontal surface of said first selective reflector.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to describe the invention and to put it into practical effect,
reference will now be made to preferred and alternate embodiments of the
invention as illustrated with reference to the accompanying drawings in
which:
FlG. 1 shows a cross-section of part of a display assembly in accordance
with a preferred embodiment of the invention;
FIG. 2 shows a cross-section of part of a display assembly in accordance
with a first alternate embodiment of the invention; and
FIG. 3 shows a cross-section of part of a display assembly in accordance
with a second alternate embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, a cross-section of part of a single display assembly
10 is shown in accordance with a preferred embodiment of the invention.
Assembly 10 comprises an electronically controllable display 11 having a
plurality of display elements 12 and sandwiched by two support plates
13,14. The display is further sandwiched by two polarizers 15,16. There
are also two selective reflectors, namely a first selective reflector 17
and a second selective reflector 18, that sandwich display 11, plates
13,14 and polarizers 15,16. Support plates 13,14 and polarizers 15,16 are
transparent media to permit passage of light and are made of either glass
or plastics. Selective reflectors 17,18 can be, for example, holographic
reflectors that are each pre-recorded with characteristics that includes a
range 19 or 20 of predetermined incident angles and an angular
transparency range (not shown) for passage of light. As is known in the
art, the angular transparency range is based on angular characteristics of
transparency of selective reflectors 17,18 and complements predetermined
incident angles to enable viewing through selective reflectors 17,18.
Assembly 10 has two opposite sides 21,22 to view indicia provided by the
plurality of display elements 12.
Display 11 provides indicia in response to driving signals from a display
driver (not shown). These driving signals actuate the plurality of display
elements 12 that can be, for example, liquid crystals. As is known in the
art, such liquid crystals are oriented in specific directions to block or
to permit passage of light when voltage driving signals are provided.
Viewing of indicia provided by display 11 through side 21 will now be
explained using incident light entering assembly 10 in a direction
indicated by an arrow 23. Incident light that is received within range 19
of predetermined incident angles passes through selective reflector 17 and
display 11. Thereafter, the incident light is reflected back by selective
reflector 18 through display 11 and selective reflector 17 to a user of
assembly 10. For viewing through side 21, reflection of the incident light
is within the angular transparency range of selective reflector 17. Thus,
range 19 of predetermined incident angles relates to selective reflector
18 and is associated with the angular transparency range of selective
reflector 17 so that the user can view the indicia provided by display 11.
As with viewing the indicia through side 21, viewing of the indicia through
side 22 also requires incident light to enter assembly 10 and be reflected
back to a viewer. However, for viewing through side 22, the incident light
has to be within range 20 of predetermined incident angles and in a
direction indicated by an arrow 24. This incident light goes through
selective reflector 18 and display 11 before being reflected back through
display 11 and selective reflector 18 by selective reflector 17. For
viewing through side 22, reflection of the incident light is within the
angular transparency range of reflector selective 18. Thus, range 20 of
predetermined incident angles relates to selective reflector 17 and is
associated with the angular transparency range of selective reflector 18
so that the viewer can view the indicia provided by display 11.
It is to be noted that ranges 19,20 of predetermined incident angles are
illustratively shown in FIG. 1 and are not meant to be angled relative to
respective inward facing horizontal surfaces 24,25 of selective reflectors
17,18 as shown. Also these ranges 19,20 of predetermined incident angles
will depend on viewing requirements as determined in accordance with use
of assembly 10. Typical ranges for desirable viewing are from ten to
fifteen degrees. Hence, for a portable electronic display device in which
viewing from opposite sides is desirable, ranges 19,20 of predetermined
incident angles can be selectively predetermined and suitably angled
relative to horizontal surfaces 24,25 so that a user can view the indicia
without having to hold the portable electronic device at awkward angles or
positions.
Referring now to FIGS. 2 and 3, a first alternate embodiment 30 and a
second alternate embodiment 40 of the invention are respectively shown. In
these alternate embodiments 30,40, assembly 10 further comprises at least
one light guide having at least one light source respectively coupled
thereto. The light guide and the light source provide illumination of
display 10 in the absence of ambient light. In alternate embodiment 30,
selective reflectors 17,18 are sandwiched by a light guide 31 at their
respective outward facing horizontal surfaces 32,33. Light guide 31 is a
single piece having an intermediate portion 34 and a light source 35 to
provide light. In alternate embodiment 40, two light guides 41,42 sandwich
selective reflectors 17,18 at horizontal surfaces 32,33 respectively.
Light sources 43,44 respectively couples to light guides 41,42 to provide
light.
Advantageously, the present invention enables indicia provided by display
11 to be viewed from opposite sides 21,22 using assembly 10. Unlike
conventional reflectors, reflectors 17,18 can selective permit passage of
incident light while reflecting back other incident light not within their
respective ranges 19,20 of predetermined incident angles. Hence, external
background on side 21 that is not related to the indicia can be alleviated
when viewing such indicia from side 22. This is because reflector 17 will
then block off most of the external background. Assembly 10 will similarly
alleviate external background on side 22 when viewing indicia from side
21.
Furthermore, because each of the ranges 19,20 of predetermined incident
angles has an associated angular transparency range for viewing from a
respective one of sides 21,22, only a user who is positioned within the
associated angular transparency range can view the indicia. Thus, the
present invention advantageously provides some degree of privacy when
viewing the indicia from either of sides 21,22.
Additionally, the present invention does not require relatively complex
driving circuitry or substantially additional costs from using two
separate display assemblies as assembly 11 uses only display 11 to provide
indicia.
It is further to be noted that although the display driver is not shown,
such a driver will be able to determine appropriate driving signals to
format the indicia when viewing from either of sides 21,22. Such
formatting is well known in the art and is easily accomplished by software
algorithms and sensors that determine relative position of assembly 10.
Hence, indicia currently displayed for one of the sides 21,22 can be
re-formatted for displaying on the other one of sides 21,22.
Although the invention has been described with reference to the above
embodiments, it is to be understood that the invention is not restricted
to the embodiments described herein.
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